A light suit? (5)
I believe the answer is:
match
I believe this clue is a double definition.
'a light' is the first definition.
(I know that match is a type of light)
'suit?' is the second definition.
(both can mean to go together)
(Other definitions for match that I've seen before include "Alliance" , "Fixture - fit with - smoker's aid" , "Striker < in suit" , "Game; lighter" , "Contest; pair" .)